Explain why the barometer cannot be used to measure this pressure and state what would happen if an attempt?

Question

A simple mercury barometer indicates a reading of 760 mmHg when used on Earth to measure an atmospheric pressure of 1.0x10^5 Pa. The pressure of air in a space orbit about the Earth is 0.9x10^5 Pa.
Explain why the barometer cannot be used to measure this pressure and state what would happen if an attempt were made to do so.

Answer 1

Actually, a mercury barometer can work in artificial gravity, i.e., centrifugal gravity. The centrifugal acceleration of each part of the mercury column is proportional to its distance from the center of rotation. You need to calculate the average centrifugal acceleration of the mercury column and multiply by the mass density of mercury.

However, I’m not sure if the vapor pressure of the mercury would exceed that of the space environment; it would depend on the temperature of the mercury. I’d have to look up the vapor pressure vs. temperature curve for mercury. The mercury might boil until it cools to its freezing point or until its vapor pressure drops below that of the space environment

Answer 2

In a mercury barometer, the pressure of the air exactly counterbalances the pressure produced by a column of mercury. Air pressure can be produced by various causes and does not necessary require any gravity. However, the pressure produced by the mercury column depends on the mercury's weight. As a result, if you took the barometer into a weightless environment, the mercury column could not produce any pressure to counterbalance the air. what would happen is that the air pressure would force the mercury back up into the tube until there is no empty space left in the tube.

Answer 3

Leonardo is right. A mercury barometer works by using air pressure to support the weight of a column of mercury. The higher the pressure, the higher the column. In orbit, there is no weight, so the barometer won't work. The mercury will probably float out of the tube in little balls.

Answer 4

I believe that Leonardo is actually correct. He is not saying that pressure is dependant upon gravity. Instead he is saying the a barometer's design is dependant upon gravity. Much like trying to determine an objects mass by using a balance, the barometer is dependant upon the pull of gravity to give the forces in question a downward direction.

Answer 5

Leonardo is almost right.

For one thing in zero gravity, the reading will be
not zero, but 1e-5/zero = infinity.

For another, vapor pressure of mercury at 20 C
is about 0.1 Pa, which significantly exceeds
ambient pressure. The mercury will be pushed
out from the U tube by the pressure of its own vapor
in the sealed leg of U and float as a lagre ball
of liquid, held together by surface tension.

Answer 6

A barometer uses gravity to measure the pressure, in orbit no gravity... Depending on the design of the barometer, if you tried to use it in a spacecraft, it should read 0 because there is no gravity acting on the mercury to create a vacuum.

Answer 7

Leonardo is wrong. pressure does not depent on gravity, because gravity is uniforamlly constant. The pressure of the air in space is smaller than that of eart, so that the displacement of themercury column in the barometer will be an opposite direction, so that the result is meaningless, and can not be read.